JP2013034997A - Build-up welding method and method for repairing metal member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for repairing a metal member, which can substantially equalize the hardness of a base metal to the hardness of a build-up welded part in a metal member that is repaired by build-up welding to suppress unevenness of the surface roughness of the metal member.SOLUTION: The method for repairing a metal member applies build-up welding to a hole of a metal member in which the hole is generated, using a welding material having a hardness lower than that of the metal member as a base metal and formed of the same sort of material as the base metal. The build-up welded part rapidly cools down in solidification and causes refinement in the crystal grain thereof, thus, the hardness of the base metal and the hardness of the build-up welded part are substantially equalized by the hardening in the refinement of the crystal grain.

Description

  The present invention relates to a build-up welding method and a metal member repair method using the same.

  In the metal mold as the metal member, the surface property of the mold part is important. Therefore, when an unnecessary hole or the like is generated in the mold portion, repair for filling the hole is performed. This repair is generally performed by overlay welding.

  Recently, various improvements have been made to the repair technique of metal members. In order to repair defects existing in the metal member or to improve the structure defect, a frictional heat is generated by the rotating rod to form a plastic fluidized layer inside the metal member. There is a repair method of stirring the inside of a member (Patent Document 1). This repair method is a method in which a friction stir welding method (Friction Stirring Weld) is applied to repair, and repairs defects near the surface of a metal member by stirring a plastic fluidized bed generated by frictional heat. However, this method is not a method of repairing the hole of the metal member by overlaying, and a dent inevitably generated on the surface of the metal member by the tip of the rotating member to be pressed is not left on the mold surface of the metal member. It is necessary to operate the rotating body.

  In addition, regarding the method of repairing the pressure-resistant surface of metal molds such as metal presses in the field, a base layer that has a high affinity for the base metal, impact load, and static load on the build-up weld with a welding rod with a different composition There is a method in which the intermediate layer and the surface layer having high hardness and not rusting are used (Patent Document 2).

  Furthermore, by reducing the Vickers hardness value of the weld metal part of the surface layer part of the welded joint where surplus is left, smaller than the Vickers hardness value of the base material, there is a method of reducing the stress concentration at the weld surplus toe part. Yes (Patent Document 3). However, since this document relates to a welded joint, it is not an overlay welding method for repairing defects such as holes.

JP 2000-15426 A Japanese Patent No. 3954752 JP 2004-337938 A

  Improvements in metal member repair technologies are often related to the improvement of the structure by welding, the enhancement of strength, the extension of life, and the minimization of distortion. Patent Documents 1 to 3 listed above also improve the soundness and strength characteristics of the structure of the welded part. The main purpose is to improve or avoid defects caused by welding.

  However, the metal member subjected to overlay welding has another problem of in-plane change in surface roughness characteristics due to the hardness difference between the welded portion and the base material. For example, when the mold is polished after the repair, the polishing unevenness may occur between the repaired part and the part other than the repaired part. Further, when the mold is subjected to a blasting process for cleaning or the like, the surface roughness after the blasting process may be different between a repaired part and a part other than the repaired part. These in-plane changes in polishing unevenness and surface roughness were directly connected to color unevenness and glossiness unevenness of a molded product manufactured using the mold. There are few improvement techniques for this problem.

  The present invention has been invented under such circumstances, and its purpose is to make the hardness of the overlay weld portion approximately equal to the hardness of the base metal after overlay welding, and to make the surface hardness in-plane uniform. An object of the present invention is to provide a build-up welding method and a repair method for a metal member using the build-up welding method.

  The overlay welding method of the present invention uses a welding material having a lower hardness than the base material and made of the same kind of material as the base material, which is a base material made of a non-quenching hardening type metal material. It is characterized by welding.

  The method for repairing a metal member according to the present invention uses a welding material made of the same kind of material as the base material, and the hole of the metal member having a hole on the surface is lower in hardness than the metal member that is the base material. Repair is performed by the above-described overlay welding method in which overlay welding is performed.

  The repair method of the metal member of this invention can work harden the build-up welding part after build-up welding. Moreover, the repair method of the metal member of this invention can be applied suitably, when the metal member which is a base material is a metal mold | die for tire shaping | molding. Furthermore, the difference in hardness between the Vickers hardness of the build-up welded portion that is the repaired portion or the build-up welded portion that is the work-hardened portion after this repair and the Vickers hardness of the base material is within 20 Is preferably 10 or less.

  According to the present invention, when performing overlay welding of a metal member that is a base material made of a non-quenching curable metal material, a welding material that is lower in hardness than the base material and made of the same material as the base material is used. Thus, the hardness of the weld metal can be made approximately equal to the hardness of the base material by crystal grain refinement hardening at the time of solidification, and as a result, the surface hardness of the metal member can be made in-plane uniform.

It is a schematic diagram which shows the cross section of the surface vicinity of the metal mold | die for tire shaping | molding. It is a graph which shows the example of the hardness of the build-up welding part in the metal mold | die for tire shaping | molding. It is a graph which shows the example of the hardness of the build-up welding part in the metal mold | die for tire shaping | molding. It is a graph which shows the example of the hardness of the build-up welding part in the metal mold | die for tire shaping | molding. It is a graph which shows the result of having performed the multivariate analysis of hardness from the result of the Example. It is typical sectional drawing of the metal mold | die which repairs. It is a graph which shows the example of the hardness of the build-up welding part in the metal mold | die for tire shaping | molding. It is a graph which shows the example of the hardness of the build-up welding part in the metal mold | die for tire shaping | molding. It is a graph which shows the example of the hardness of the build-up welding part in the metal mold | die for tire shaping | molding. It is a graph which shows the result of having performed the multivariate analysis of hardness from the result of the Example. .

Hereinafter, the overlay welding method and the metal member repair method of the present invention will be described in more detail.
The overlay welding method and the repair method for a metal member of the present invention are intended for a metal member that is a base material for overlay welding, which is made of a non-quenching hardening type metal material. The non-quenching curable metal material refers to a metal material that does not undergo quench hardening. There are ferritic steel, cast steel, and cast iron among metal materials that can be hardened by quenching, but metal materials that age harden by rapid cooling after solution treatment are not included in the metal materials that are hardened by hardening. To do. The hardened and hardened metal material is locally cured in the vicinity of the weld during overlay welding, so it is difficult to achieve in-plane uniformity of the surface hardness of the metal member as expected in the present invention. Steel materials as hardened and hardened metal materials have a wide hardness range for the base materials and welding materials used (Vickers hardness Hv is 100 to 200), so adjustment to achieve in-plane uniformity of the surface hardness of metal members Is difficult. Furthermore, since steel materials are harder than non-ferrous metal materials, a large stress is required for processing for work hardening as described later.

  Therefore, in the present invention, the metal material that is not hardened by hardening means to exclude ferritic steel, cast steel, and cast iron among the metal materials. Specific examples of the metal material to be hardened by hardening include non-ferrous metal aluminum alloys and copper alloys. The Vickers hardness Hv of the aluminum alloy is about 50 to 100, and the hardness range is narrower than that of the steel material. These aluminum alloys and copper alloys are used as mold materials such as tire molds.

  When repairing a metal member, which is a base material made of the non-quenching curable metal material, by overlay welding, a welding material having a lower hardness than the base material and made of the same type of material as the base material is used. The same kind of material as the base material refers to a material having the same main component as the base material, and is a so-called common material or common metal. For example, when the base material is an aluminum alloy, the welding material is pure aluminum or an aluminum alloy whose main component is aluminum.

  When repairing a hole generated in a metal member such as a mold by overlay welding using a welding material whose hardness is lower than that of the base material, the overall size of the metal member to be repaired is used. The size of the repaired part is extremely small. Therefore, the weld metal is rapidly cooled by the base material and solidified during the overlay welding. The rapidly cooled weld metal has a small crystal grain size, that is, a refined crystal structure. Regarding the relationship between the crystal grain size and hardness of the crystal structure, the hardness increases as the crystal grain size decreases as shown by the Hall-Petch rule. Therefore, since the hardness of the rapidly cooled weld metal is higher than the hardness of the welding material, it is possible to make the hardness of the build-up weld portion, which is a repaired portion, approximately equal to the hardness of the base material.

  The degree of increase in hardness of the overlay welding portion is a function of the welding heat input per unit time, the welding amount, and the basic hardness of the welding rod as the welding material. Therefore, in order to approximately equalize the hardness of the build-up welded portion and the hardness of the base metal, these relational expressions are obtained, and based on the relational expression, the hardness of the build-up welded part after repair is equal to the hardness of the base metal. Overlay welding is performed under welding conditions that are equivalent or have a hardness difference within a predetermined range. Thereby, in-plane uniformity of the surface hardness of the metal member can be achieved, and as a result, the surface roughness of the metal member can be made uniform. Therefore, the hole produced in the metal member can be effectively repaired by applying the overlay welding method as described above to the repair of the metal member.

  If the increase in the hardness of the weld overlay does not reach the hardness of the base metal, the weld overlay is processed after overlay welding, plastic strain is introduced, and work hardening is performed. Can be made equal to the hardness of the base material. As a specific example of processing, the build-up welded portion may be hit with a hammer or a punch. Further, hitting the weld overlay with a hammer or a punch has an effect of preventing the weld metal in the weld overlay from being lost due to some impact or pressure. But the processing means for work hardening the build-up welding part is not limited to this. In the repair of the mold surface of the mold, processing is performed so that unnecessary plastic strain is not introduced into portions other than the build-up welded portion that is the repaired portion.

  The increase in hardness of the build-up weld due to work hardening is a function of the hardness of the build-up weld, the weld material (work hardening index, work hardening diameter), and the amount of added plastic strain. Therefore, these relational expressions are obtained, and the build-up welded part is processed so that the hardness of the welded welded part after processing is equivalent to the hardness of the base material based on the relational expression.

  The repair method of the present invention is suitable for use in repairing a tire molding die. Generally, an aluminum alloy is used for the tire mold. Also, in the mold for tire molding, when the blade is embedded in the mold to form the sipe of the tread surface portion of the tire, the mold surface of the mold is repaired so as to fill the hole for pin fixing the blade. There is a need to. Furthermore, the mold surface of the mold may be repaired so as to fill unnecessary blade holes. Furthermore, when a tire molding die is manufactured by casting, holes due to shrinkage cavities and inclusions may be formed on the mold surface. It is preferable to apply the repair method of the present invention to repairs in these cases. By applying the repair method of the present invention, the size of the hole to be repaired is much smaller than the overall size of the tire molding die, so that the weld metal is quenched and hardened by the tire molding die during overlay welding. Rises. In addition, the mold for tire molding needs to polish the mold surface after repair, and since the mold surface is blasted for cleaning etc., if the hardness of the repaired part and other parts is different, There is a problem of causing uneven color and glossiness of the tire as a product. The present invention can solve this problem.

  In the repair method of the present invention, the difference in Vickers hardness between the hardness of the build-up welded portion and the hardness of the base material is preferably 20 or less. The hardness of the build-up welded portion is the hardness after build-up welding when the above-described work hardening is not performed, and the hardness after work hardening when the work hardening is performed. By setting the Vickers hardness to 20 or less, in-plane distribution of surface roughness can be made uniform when the metal member is a mold. The difference in hardness includes both cases where the hardness of the base material is higher and lower than the hardness of the build-up welded portion, and the absolute value of the difference in hardness is preferably 20 or less. More preferably, it is within 10 in terms of Vickers hardness.

  A tire molding die was used as a metal member as a base material. The tire molds used were made of three materials: AC2B (Al—Cu—Si alloy), AC4C (Al—Si—Mg alloy) and AC7A (Al—Mg alloy). Moreover, the welding rod used as the welding material used was 3 types of A-1100BY (pure Al type), A-4043BY (Al-Si type), and A-5356 (Al-Mg type). A hole having a diameter of 1 mm and a depth of 1 mm was formed on the surface of these base materials, and overlay welding was performed to repair the hole generated on the surface of the tire molding die.

  The welding machine used was a Spark Depot (Model 300) from Technocoat Corporation. This welding machine is an apparatus that can perform overlay welding in a narrow region by applying a high voltage while holding and rotating a welding rod with a chuck.

  After the build-up welding, the build-up weld portion and its periphery were cut out in the depth direction from the surface, and the Vickers hardness was measured at each of the weld surface, the weld center, and the weld interface in the cross section. The load at the time of hardness measurement was 200 g. In FIG. 1, the hardness measurement locations in the welded portion 1a of the tire molding die 1 are illustrated as a welded portion surface p1, a welded portion center p2, and a welded portion interface p3. In addition, the color unevenness on the tire surface after the tire was molded using these molds was subjected to sensory evaluation. This sensory evaluation is marked with ◎ when there is no color unevenness, ◯ when there is almost no color unevenness, and when the product is commercially available, with moderate color unevenness, and △ mark when the evaluation is not good. In the case of an evaluation that is not good at all, it was marked with a cross.

  FIG. 2 is a graph showing the hardness of the built-up weld when the mold material is AC2B. Table 1 shows the evaluation results of the color unevenness on the surface of the tire formed by using the AC2B mold together with the hardness difference on the surface of the weld overlay.

  2 and Table 1, when the material of the mold is AC2B, the difference in hardness between the surface hardness of the weld and the base material hardness is within 10 by using A-4043 or A-5356 for the welding rod. there were. Therefore, a good result was obtained in which there was no color unevenness in the tire. On the other hand, when A-1100 was used for the welding rod, the hardness difference exceeded 20 and the evaluation of the uneven color of the tire was bad.

  FIG. 3 is a graph showing the hardness of the built-up weld when the mold material is AC4C. Table 2 shows the evaluation results of color unevenness on the surface of the tire formed by using this AC4C mold together with the hardness difference on the surface of the weld overlay.

  3 and Table 2, when the material of the mold is AC4C, the difference in hardness between the hardness of the surface of the weld and the base material hardness was within 10 by using A-4043 for the welding rod. Therefore, a good result was obtained in which there was no color unevenness in the tire. Moreover, when A-1100 or A-5356 was used for the welding rod, the hardness difference was within 20 and there was almost no color unevenness.

  FIG. 4 is a graph showing the hardness of the built-up weld when the mold material is AC7A. Table 3 shows the evaluation results of the uneven color on the surface of the tire formed by using the AC7A mold together with the hardness difference on the surface of the weld overlay.

  4 and Table 3, when the material of the mold is AC7A, the difference in hardness between the hardness of the weld surface and the base material hardness was within 10 by using A-4043 for the welding rod. Therefore, a good result was obtained in which there was no color unevenness in the tire. Moreover, when A-1100 was used for the welding rod, the hardness difference was within 20 and there was almost no color unevenness. Furthermore, when A-5356 was used for the welding rod, the hardness difference exceeded 20 and the color unevenness was moderate.

  In addition, multivariate analysis was performed with welding seconds, build-up amount, hardness of welding material as explanatory variables, and hardness of metal surface as objective variable. Each regression coefficient was as shown in FIG.

  When actually applied, the hardness of the target metal surface can be obtained by changing each condition.

  In the examples described below, after repairing the mold surface of the tire molding die by build-up welding, the build-up weld portion was work-hardened to increase the hardness of the build-up weld portion. The tire molds used were made of three materials, AC2B, AC4C, and AC7A, as in the above-described examples. Moreover, the used welding rod was made into three types, A-1100BY, A-4043BY, and A-5356 like the Example mentioned above.

  As shown in FIG. 6, a shallow hole h1 (depth: 0.8 mm) by punching, a diameter of 1 mm and a depth of 1 mm by boring is formed on the surface of the base material 2 where the thickness is 10 mm. Three types of holes, h2 and a hole h3 having a diameter of 1 mm and a depth of 2 mm, were formed, and overlay welding was performed to repair the holes. As the welding machine, the same Technode Corporation Spark Depot (Model 300) as in the above-described embodiment was used.

  After build-up welding, the build-up welded portion was hit with an air hammer for 5 seconds, and the build-up welded portion was work-hardened. Then, the build-up welding part and its circumference | surroundings were cut out from the surface in the depth direction, and the Vickers hardness was measured in each of the weld part surface in the cross section, the weld part center, and the weld part interface. The load at the time of hardness measurement was 200 g.

  The results of the hardness measurement are shown in graphs in FIGS. 7 to 9 for each type of welding rod according to the average hardness of the welded portion. FIG. 7 shows an example in which the welding rod is A-1100BY. FIG. 8 shows an example in which the welding rod is A-4043BY. FIG. 9 shows an example in which the welding rod is A-5356BY. From these drawings, it is understood that the build-up welded portion can be work-hardened by hitting the build-up welded portion after the build-up welding. Therefore, even if the build-up welded portion has a hardness higher than the hardness of the welding rod due to crystal grain refinement, it is effective to work harden the build-up welded portion if the hardness of the base metal is insufficient. I understand that there is.

  Sensory evaluation was performed on the color unevenness of the tire surface after the tire was molded using the mold after work hardening of the build-up welded part by repair. This sensory evaluation criterion is the same as that in the above-described example.

  Table 5 shows the evaluation of uneven color on the tire surface when the mold material is AC2B, Table 6 shows the case where the mold material is AC4C, and Table 7 shows the case where the mold material is AC7A. The results are shown together with the hardness difference between the surface of the overlay welding portion of the mold and the base material.

  From the results of Tables 5 to 7, the overlay welding part is the mother by adjusting the welding rod material and the presence / absence of work hardening and the degree of work hardening appropriately according to the material of the mold and the depth of the hole to be repaired. The hardness difference with the material was reduced, and the color unevenness on the surface of the tire molded by this mold could be suppressed.

  In addition, multivariate analysis was performed with the work hardening index and strain applied as explanatory variables and the hardness of the metal surface as the objective variable. Each regression coefficient was as shown in FIG.

  When actually applied, the hardness of the target metal surface can be obtained by changing each condition.

  In the above description, the example in which the material of the metal member is an aluminum alloy has been described. However, the present invention is not limited to the description of the example, and the metal member is made of a non-quenching curable metal material, and the welding material is Any material that can be implemented by the same type of material as the non-quenching curable metal material can be used. For example, even when the metal member is a copper alloy, the overlay welding method and the repair method of the present invention can be applied.

1: Tire molding die 2: Base material

Claims (6)

  A metal member, which is a base material made of a non-quenching hardening type metal material, has a hardness lower than that of the base material and is subjected to overlay welding using a welding material made of the same kind of material as the base material Prime welding method.   A repair method for a metal member, comprising repairing the hole of the metal member having a hole on the surface by the overlay welding method according to claim 1.   The method for repairing a metal member according to claim 2, wherein after the build-up welding, the build-up weld portion is work-hardened.   The method for repairing a metal member according to claim 2 or 3, wherein the metal member is a tire molding die.   The method for repairing a metal member according to any one of claims 2 to 4, wherein the difference in Vickers hardness between the base material and the overlay welded portion is 20 or less.   The method for repairing a metal member according to any one of claims 2 to 5, wherein a difference in Vickers hardness between the base material and the overlay welding portion is within 10 or less.

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